22 DurryospoNoiOif;. 



me for an extravagant sum (£200), because they contained tlie ci-ab that 

 formed llieni." Sir \\'ya'illk Thomson relates similar facts * and adds : " It is 

 singular tliat while Pahjthoa fatna is as constantly associated with examples of 

 Hyalonema from the coast of Portugal as with those of Japan, no commen- 

 sal crustacean has been found in any of the Atlantic specimens of Euplec- 

 TELLA." DoDERLEiN has described f a Japanese lithistid sponge having a surface 

 covered with small protuberances -within each of which dwells a cirripede of 

 the genus Acasta. The little crustacean communicates with the outer world 

 through a small opening in the reticulum which is closed at its death. 



Amon<r the Dictyosi'oxoid.e we have observed several instances of vermi- 

 form tube-fillings complicated with the imj)ressious of the reticulum and dis- 

 tinctly pronounced on the internal casts of the sponges. These tubes are 

 shown in the figure of Hydnoceras tuberosum, var. gloasema, on Plate IX 

 (fig, 2), and in the illustration of Prismodictya teluni, on Plate XVII 

 (figs. 3, 9, 10). In all probability these markings indicate the presence of 

 an annelid symbiotic with these sponges. 



Affinities of the Dictyospongidae. 



In seeking a proper definition of the family Dictyospongid^, it is necessary 

 to consider its relations to, and differences from the other admitted families of 

 the Lyssacine sponges. On account of the insufliciency of knowledge concern- 

 ing the spicular structure of these fossils, but few serious attempts have been 

 made to establish their systematic position. Hinde, in 1883, regarded them 

 as Dictyonina, and placed the genus Dictyopiiyton in the family Stauuoder- 

 MiD^;J in 1887,§ he included that genus in his proposed family Proto- 

 SPONGiDiE. These opinions were, however, based upon internal sandstone 

 casts in which all traces of the spicular elements had been obliterated. 



Raufp has defined the family very satisfactorily,^ placing it among the 

 Lyssacina. His characterization of it is in the following terms : " Funnel- 

 shaped, cylindrical or prismatic sponges with thin walls, often raised into 

 nodes or ridges; skeleton very regularly reticulated, forming, as in 

 the Protospongid^, quadrate or sub-quadrate meshes of different series, 

 enclosing one another. The frame-work is composed of bundles of fine 

 spicules, but whether these spicules are stauractins | \vith their rays lying 



• The Atlantic, vol. 1, p. 141, 1878. 



 Zeitschr. fiir wissensch. Zoologie, vol. xl, 1840. See also Raui'F, Pal.ieospongiologie, part 1, p. 140. 

 % Catalogoe of the Fossil Sponges of tbe British Museum, p. 130, 1883. 



$ Monograph British Fossil Sponges, p. 90. 

 fl Palaeospongiologie, p. 189, 1893. 



II The terms "stauractins" and "cruciform spicules" are used interchangeably for any hexactine 

 spicules showing evidence of branches. 



